Synthesis, biological activity and multiscale molecular modeling studies of bis-coumarins as selective carbonic anhydrase IX and XII inhibitors with effective cytotoxicity against hepatocellular carcinoma

Structural modification strategies of triazoles in anticancer drug development

The triazole functional group plays a pivotal role in the composition of biomolecules with potent anticancer activities, including numerous clinically approved drugs. The strategic utilization of the triazole fragment in the rational modification of lead compounds has demonstrated its ability to improve anticancer activities, enhance selectivity, optimize pharmacokinetic properties, and overcome resistance. There has been significant interest in triazole-containing hybrids in recent years due to their remarkable anticancer potential. However, previous reviews on triazoles in cancer treatment have failed to provide tailored design strategies specific to these compounds. Herein, we present an overview of design strategies encompassing a structure-modification approach for incorporating triazoles into hybrid molecules. This review offers valuable references and briefly introduces the synthesis of triazole derivatives, thereby paving the way for further research and advancements in the field of effective and targeted anticancer therapies.

3,3'-((3,4,5-trifluoropHenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) inhibit lung cancer cell proliferation and migration

Lung cancer is a major public health challenge and, despite therapeutic improvements, is the first leading cause of cancer worldwide. The current cure rate from advanced cancer treatment is excessively low. Therefore, it is of great importance to identify novel, potent and less toxic anticancer agents for the treatment of lung cancer. The aim of our research is to synthesize a new biscoumarin 3,3'-((3,4,5-trifluorop -phenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (C35) as an anticancer agent. C35 was simply prepared by 4-hydroxycoumarin and 3,4,5-trifluorobenzaldehyde under ethanol and its structure was analyzed by spectroscopic analyses. The anti-proliferation effect of C35 was detected using CCK-8 assay. Migration abilities were measured by Transwell assay. The expression of correlated proteins was determined by Western blot. The results showed that C35 displayed strong cytostatic effects on lung cancer cell proliferation. In addition, C35 possessed a significant inhibition of migration by reducing the expression of matrix metalloproteinases-2 (MMP-2) and MMP-9 in lung cancer cells. Furthermore, C35 treatment suppressed the phosphorylation of p38 in lung cancer cells. Moreover, in vivo experiments were carried out, in which we treated Lewis tumor-bearing C57 mice via intraperitoneal injection of C35. Results showed that C35 inhibited tumor growth in vivo. In conclusion, our study demonstrated the anticancer activity of C35 via suppression of lung cancer cell proliferation and migration, which is possibly involved with the inhibition of the p38 pathway.

Anticancer mechanism of coumarin-based derivatives

The structural motif of coumarins is related with various biological activities and pharmacological properties. Both natural coumarin extracted from various plants or a new coumarin derivative synthesized by modification of the basic structure of coumarin, in vitro experiments showed that coumarins are a promising class of anti-tumor agents with high selectivity. Cancer is a complex and multifaceted group of diseases characterized by the uncontrolled and abnormal growth of cells in the body. This review focuses on the anticancer mechanism of various coumarins synthesized and isolated in more than a decade. Isopentenyloxycoumarins inhibit angiogenesis by reducing CCl2 chemokine levels. Ferulin C is a potent colchicine-binding agent that destabilizes microtubules, exhibiting antiproliferative and anti-metastatic effects in breast cancer cells through PAK1 and PAK2-mediated signaling. Trimers of triphenylethylene-coumarin hybrids demonstrated significant proliferation inhibition in HeLa, A549, K562, and MCF-7 cell lines. Platinum(IV) complexes with 4-hydroxycoumarin have the potential for high genotoxicity against tumor cells, inducing apoptosis in SKOV-3 cells by up-regulating caspase 3 and caspase 9 expression. Derivatives of 3-benzyl coumarin seco-B-ring induce apoptosis, mediated through the PI3K/Akt/mTOR signaling pathway. Sesquiterpene coumarins inhibit the efflux pump of multidrug resistance-associated protein. Coumarin imidazolyl derivatives inhibit the aromatase enzyme, a major contributor to estrogen overproduction in estrogen-dependent breast cancer.

pH regulators and their inhibitors in tumor microenvironment

As an important characteristic of tumor, acidic tumor microenvironment (TME) is closely related to immune escape, invasion, migration and drug resistance of tumor. The acidity of the TME mainly comes from the acidic products produced by the high level of tumor metabolism, such as lactic acid and carbon dioxide. pH regulators such as monocarboxylate transporters (MCTs), carbonic anhydrase IX (CA IX), and Na+/H+ exchange 1 (NHE1) expel protons directly or indirectly from the tumor to maintain the pH balance of tumor cells and create an acidic TME. We review the functions of several pH regulators involved in the construction of acidic TME, the structure and structure-activity relationship of pH regulator inhibitors, and provide strategies for the development of small-molecule antitumor inhibitors based on these targets.

Novel 2-(hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide based thiosemicarbazides as potent and selective inhibitors of tumor-associated human carbonic anhydrase IX and XII: Synthesis, cytotoxicity, and molecular modelling studies

In the pursuit of discovering new selective carbonic anhydrase (CA, EC 4.2.1.1) inhibitors, a small collection of novel thiosemicarbazides (5a-5t) were designed and synthesized starting from 2-(hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide which was evaluated as a potent inhibitor of different CA isoforms in a previous study. The newly synthesized compounds were examined against four human carbonic anhydrases (hCA), namely transmembrane tumor-related hCA IX/XII and cytosolic widespread off-targets hCA I/II. In enzyme inhibition assays, all nineteen compounds display up to ∼340-fold selectivity for hCA IX/XII over off-target isoforms hCA I/II. Four compounds have enzyme inhibition values (Ki) lower than 10 nM against tumor-associated isoforms hCA IX/XII including two compounds in the subnanomolar range (5r and 5s; hCA XII; Ki: 0.69 and 0.87 nM). The potential binding interactions of the most potent compounds against hCA IX and XII, compounds 5s and 5r, respectively, were investigated using ensemble docking and molecular dynamics studies. Cell viability assays using human colorectal adenocarcinoma cell line HT-29 and healthy skin fibroblasts CCD-86Sk show that compound 5e selectively inhibits HT-29 cancer cell proliferation (IC50: 53.32 ± 7.74 µM for HT-29; IC50: 74.64 ± 14.15 µM for CCD-986Sk). Finally, Western blot assays show that compounds 5e and 5r significantly reduce the expression of hCA XII in HT-29 cells. Moreover, 5e shows better cytotoxic activity in hypoxia compared to normoxic conditions. Altogether, the newly designed compounds show stronger inhibition of the tumor-associated hCA IX and XII isoforms and several tested compounds show selective cytotoxicity as well as downregulation of hCA XII expression.

Exploring the potency of diazo-coumarin containing hybrid molecules: Selective inhibition of tumor-associated carbonic anhydrase isoforms IX and XII

This study introduces a series of ten hybrid molecules DK(1-10), which combine diazo and coumarin moieties along with diverse aromatic substitutions. The primary objective was to evaluate the inhibitory capabilities of these compounds against four prominent isoforms: the cytosolic hCA I and II, as well as the tumor-associated membrane-bound hCA IX and XII. Impressively, the majority of the tested compounds exhibited significant inhibition activity against the tumor-associated isoforms hCA IX and XII, with KI values ranging from 29.2 to 293.3 nM. Notably, compound DK-8 displayed particularly robust inhibitory activity against the tumor-associated membrane-bound isoforms, hCA IX and XII, yielding KI values of 32.5 and 29.2 nM, respectively. Additionally, another derivative, DK-9, containing a primary sulfonamide, exhibited notable inhibition against hCA XII with a KI value of 36.4 nM. This investigation aimed to explore the structure-activity relationships within these compounds, shedding light on how various substitutions and structural components influence their inhibitory potential. As a result, these compounds present promising candidates for further exploration in medicinal and pharmacological research. Their ability to selectively inhibit specific isoforms, particularly those associated with hypoxic tumors, suggests their potential as foundational compounds for the development of novel therapeutic agents.

Potent carbonic anhydrase I, II, IX and XII inhibition activity of novel primary benzenesulfonamides incorporating bis-ureido moieties

A novel series of twelve aromatic bis-ureido-substituted benzenesulfonamides was synthesised by conjugation of aromatic aminobenzenesulfonamides with aromatic bis-isocyanates. The obtained bis-ureido-substituted derivatives were tested against four selected human carbonic anhydrase isoforms (hCA I, hCA II, hCA IX and hCA XII). Most of the new compounds showed an effective inhibitory profile against isoforms hCA IX and hCA XII, also having some selectivity with respect to hCA I and hCA II. The inhibition constants of these compounds against isoforms hCA IX and XII were in the range of 6.73-835 and 5.02-429 nM, respectively. Since hCA IX and hCA XII are important drug targets for anti-cancer/anti-metastatic drugs, these effective inhibitors reported here may be considered of interest for cancer related studies in which these enzymes are involved.

Tail-Approach-Based Design and Synthesis of Coumarin-Monoterpenes as Carbonic Anhydrase Inhibitors and Anticancer Agents

In this study, sixty novel coumarin-monoterpene compounds were synthesized in two series [thirty-two compounds (12-43) bearing a triazole ring in the first series, and twenty-eight compounds (44-71) bearing an alkyl chain in the second one]. Their inhibitory effects on the human carbonic anhydrase (hCA) isoforms I, II, IX, and XII and anticancer potentials were determined. All synthesized molecules selectively inhibited CA IX and XII. 23 and 42 were found to be the strongest inhibitors, with K _i values of 1.9 nM against hCA IX. Also, 70 showed the highest inhibitory activity with a K _i value of 4.9 nM against hCA XII. Moreover, their cytotoxic effects on colon adenocarcinoma (HT-29), prostate adenocarcinoma (PC-3), and breast adenocarcinoma (MCF-7) cell lines were evaluated. According to the cytotoxicity results, 14 (IC₅₀ = 2.48 μM) and 63 (IC₅₀ = 3.91 μM) exhibited the highest cytotoxicity on the MCF-7 cells, while 23 showed the strongest cytotoxic effect on both PC-3 (IC₅₀ = 9.40 μM) and HT-29 (IC₅₀ = 12.10 μM) cell lines. 14, 23, and 66 decreased CA IX and CA XII protein expression in HT-29 cells, while 23 and 66 showed the strongest reduction of both CA IX and CA XII in MCF-7 cells. All of the selected compounds increased total apoptosis in a concentration-dependent manner in HT-29 and MCF-7 cells. 14 has the strongest apoptotic effect in MCF-7 cells. 23 increased early apoptosis primarily, while 14 and 66 increased total apoptosis in HT-29. In addition, PI/Hoechst staining proves that apoptotic cells are increased in HT-29 with an effect of 14, 23, and 66. As a result of the modeling studies, it has been shown that only the open coumarin form of the compounds can interact directly with the active-site Zn²⁺ ion. It has been shown that coumarin-monoterpene structures with different alkyl and monoterpene groups both specifically inhibit CA IX and XII and exhibit specific cytotoxicity in different cell lines.

Novel Insights on Human Carbonic Anhydrase Inhibitors Based on Coumalic Acid: Design, Synthesis, Molecular Modeling Investigation, and Biological Studies

Human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms IX and XII are overexpressed in solid hypoxic tumors, and they are considered as prognostic tools and therapeutic targets for cancer. Based on a molecular simplification of the well-known coumarin scaffold, we developed a new series of derivatives of the pyran-2-one core. The new compounds are endowed with potent and selective inhibitory activity against the tumor-related hCA isoforms IX and XII, in the low nanomolar range, whereas they are inactive against the two cytosolic off-targets hCA I and II. The compounds exhibiting the best hCA inhibition were further investigated against the breast adenocarcinoma cell line (MCF7) in hypoxic conditions, evaluating their ability to eventually synergize with doxorubicin. The compounds’ biocompatibility on healthy cells was also tested and confirmed on Human Gingival Fibroblasts (HGFs). Furthermore, the possible binding mode of all compounds to the active site of the tumor-associated human CA IX was investigated by computational techniques which predicted the binding conformations and the persistency of binding poses within the active site of the enzyme, furnishing relevant data for the design of tight binding inhibitors.

New solid phase methodology for the synthesis of biscoumarin derivatives: experimental and in silico approaches

The simple and greener one-pot approach for the synthesis of biscoumarin derivatives using catalytic amounts of nano-MoO₃ catalyst under mortar-pestle grinding was described. The use of non-toxic and mild catalyst, cost-effectiveness, ordinary grinding, and good to the excellent yield of the final product makes this procedure a more attractive pathway for the synthesis of biologically remarkable pharmacophores. Accordingly, biscoumarin derivatives were successfully extended in the developed protocols. Next, a computational investigation was performed to identify the potential biological targets of this set of compounds. In this case, first, a similarity search on different virtual libraries was performed to find an ideal biological target for these derivatives. Results showed that the synthesized derivatives can be α-glucosidase inhibitors. In another step, molecular docking studies were carried out against human lysosomal acid-alpha-glucosidase (PDB ID: 5NN8) to determine the detailed binding modes and critical interactions with the proposed target. In silico assessments showed the gold score value in the range of 17.56 to 29.49. Additionally, molecular dynamic simulations and the MM-GBSA method of the most active derivative against α-glucosidase were conducted to study the behavior of selected compounds in the biological system. Ligand 1 stabilized after around 30 ns and participated in various interactions with Trp481, Asp518, Asp616, His674, Phe649, and Leu677 residues.

In the footsteps of an inhibitor unbinding from the active site of human carbonic anhydrase II

The crystal structure of human carbonic anhydrase (HCA) II bound to an inhibitor molecule, 6-hydroxy-2-thioxocoumarin (FC5), shows FC5 to be located in a hydrophobic pocket at the active site. The present work employs classical molecular dynamics (MD) simulation to follow the FC5 molecule for 1 μs as it unbinds from its binding location, adopts the path of substrate/product diffusion (path 1) to leave the active site at around 75 ns. It is then found to undergo repeated binding and unbinding at different locations on the surface of the enzyme in water. Several transient excursions through different regions of the enzyme are also observed prior to its exit from the active site. These transient paths are combined with functionally relevant cavities/channels to enlist five additional pathways (path 2-6). Pathways 1-6 are subsequently explored using steered MD and umbrella sampling simulations. A free energy barrier of 0.969 kcal mol^-1 is encountered along path 1, while barriers in the range of 0.57-2.84 kcal mol^-1 are obtained along paths 2, 4 and 5. We also analyze in detail the interaction between FC5 and the enzyme along each path as the former leaves the active site of HCA II. Our results indicate path 1 to be the major exit pathway for FC5, although competing contributions may also come from the paths 2, 4 and 5.Communicated by Ramaswamy H. Sarma.

2-Aminobenzoxazole-appended coumarins as potent and selective inhibitors of tumour-associated carbonic anhydrases

We have carried out the design, synthesis, and evaluation of a small library of 2-aminobenzoxazole-appended coumarins as novel inhibitors of tumour-related CAs IX and XII. Substituents on C-3 and/or C-4 positions of the coumarin scaffold, and on the benzoxazole moiety, together with the length of the linker connecting both units were modified to obtain useful structure-activity relationships. CA inhibition studies revealed a good selectivity towards tumour-associated CAs IX and XII (K_i within the mid-nanomolar range in most of the cases) in comparison with CAs I, II, IV, and VII (K_i > 10 µM); CA IX was found to be slightly more sensitive towards structural changes. Docking calculations suggested that the coumarin scaffold might act as a prodrug, binding to the CAs in its hydrolysed form, which is in turn obtained due to the esterase activity of CAs. An increase of the tether length and of the substituents steric hindrance was found to be detrimental to in vitro antiproliferative activities. Incorporation of a chlorine atom on C-3 of the coumarin moiety achieved the strongest antiproliferative agent, with activities within the low micromolar range for the panel of tumour cell lines tested.

Coumarins and Gastrointestinal Cancer: A New Therapeutic Option?

Cancers of the gastrointestinal (GI) tract are often life-threatening malignancies, which can be a severe burden to the health care system. Globally, the mortality rate from gastrointestinal tumors has been increasing due to the lack of adequate diagnostic, prognostic, and therapeutic measures to combat these tumors. Coumarin is a natural product with remarkable antitumor activity, and it is widely found in various natural plant sources. Researchers have explored coumarin and its related derivatives to investigate their antitumor activity, and the potential molecular mechanisms involved. These mechanisms include hormone antagonists, alkylating agents, inhibitors of angiogenesis, inhibitors of topoisomerase, inducers of apoptosis, agents with antimitotic activity, telomerase inhibitors, inhibitors of human carbonic anhydrase, as well as other potential mechanisms. Consequently, drug design and discovery scientists and medicinal chemists have collaborated to identify new coumarin-related agents in order to produce more effective antitumor drugs against GI cancers. Herein, we summarize the therapeutic effects of coumarin and its derivatives against GI cancer.

Synthesis, Crystal Structure, Inhibitory Activity and Molecular Docking of Coumarins/Sulfonamides Containing Triazolyl Pyridine Moiety as Potent Selective Carbonic Anhydrase IX and XII Inhibitors

In this work, two classes of Carbonic Anhydrase (CA) inhibitors, sulfonamide and coumarin derivatives linked to pyta moiety (2a-b) and their corresponding rhenium complexes (3a-b), were designed. These compounds were synthesized and fully characterized by classical analytical methods and X-ray diffraction. All the synthesized compounds were evaluated for their inhibitory activity against the hCA isoforms I, II, IX and XII. They exhibited high inhibitory activities in the range of nanomolar for both hCA IX and hCA XII isoforms. The sulfonamide compound 2a showed the strongest inhibition against the tumour-associated hCA IX isoform with a Ki of 11.7 nM. The tumour-associated isoforms hCA IX and hCA XII were selectively inhibited by all the coumarin derivatives, with inhibition constants ranging from 12.7 nM (2b) to 44.5 nM (3b), while the hCA I and II isoforms were slightly inhibited (in the micromolar range), as expected. In terms of selectivity, compared to previously published rhenium complex-based CA inhibitors, complex 3b showed one of the highest selectivities against hCA IX and hCA XII compared to the off-target isoforms hCA I and hCA II, making it a potential anti-cancer drug candidate. Molecular docking calculations were performed to investigate the inhibition profiles of the investigated compounds at the tumour-associated hCA IX active site and to rationalize our results.

Tetrahydroquinazole-based secondary sulphonamides as carbonic anhydrase inhibitors: synthesis, biological evaluation against isoforms I, II, IV, and IX, and computational studies

A library of variously decorated N-phenyl secondary sulphonamides featuring the bicyclic tetrahydroquinazole scaffold was synthesised and biologically evaluated for their inhibitory activity against human carbonic anhydrase (hCA) I, II, IV, and IX. Of note, several compounds were identified showing submicromolar potency and excellent selectivity for the tumour-related hCA IX isoform. Structure-activity relationship data attained for various substitutions were rationalised by molecular modelling studies in terms of both inhibitory activity and selectivity.

Synthesis of New Biscoumarin Derivatives, In Vitro Cholinesterase Inhibition, Molecular Modelling and Antiproliferative Effect in A549 Human Lung Carcinoma Cells

A series of novel C4-C7-tethered biscoumarin derivatives (12a–e) linked through piperazine moiety was designed, synthesized, and evaluated biological/therapeutic potential. Biscoumarin 12d was found to be the most effective inhibitor of both acetylcholinesterase (AChE, IC₅₀ = 6.30 µM) and butyrylcholinesterase (BChE, IC₅₀ = 49 µM). Detailed molecular modelling studies compared the accommodation of ensaculin (well-established coumarin derivative tested in phase I of clinical trials) and 12d in the human recombinant AChE (hAChE) active site. The ability of novel compounds to cross the blood–brain barrier (BBB) was predicted with a positive outcome for compound 12e. The antiproliferative effects of newly synthesized biscoumarin derivatives were tested in vitro on human lung carcinoma cell line (A549) and normal colon fibroblast cell line (CCD-18Co). The effect of derivatives on cell proliferation was evaluated by MTT assay, quantification of cell numbers and viability, colony-forming assay, analysis of cell cycle distribution and mitotic activity. Intracellular localization of used derivatives in A549 cells was confirmed by confocal microscopy. Derivatives 12d and 12e showed significant antiproliferative activity in A549 cancer cells without a significant effect on normal CCD-18Co cells. The inhibition of hAChE/human recombinant BChE (hBChE), the antiproliferative activity on cancer cells, and the ability to cross the BBB suggest the high potential of biscoumarin derivatives. Beside the treatment of cancer, 12e might be applicable against disorders such as schizophrenia, and 12d could serve future development as therapeutic agents in the prevention and/or treatment of Alzheimer’s disease.

Quinoline-sulfamoyl carbamates/sulfamide derivatives: Synthesis, cytotoxicity, carbonic anhydrase activity, and molecular modelling studies

Carbonic anhydrase (CA) IX, and XII isoforms are known to be highly expressed in various human tissues and malignancies. CA IX is a prominent target for some cancers because it is overexpressed in hypoxic tumors and this overexpression leads to poor prognosis. Novel twenty-seven compounds in two series (sulfamoylcarbamate-based quinoline (2a-2o) and sulfamide-based quinoline (3a-3l)) were synthesized and characterized by means of IR, NMR, and mass spectra. Their inhibitory activities were evaluated against CA I, CA II, CA IX, and CA XII isoforms. 2-Phenylpropyl (N-(quinolin-8-yl)sulfamoyl)carbamate (2m) exhibited the highest hCA IX inhibition with the K_i of 0.5 µM. In addition, cytotoxic effects of the synthesized compounds on human colorectal adenocarcinoma (HT-29; HTB-38), human breast adenocarcinoma (MCF7; HTB-22), human prostate adenocarcinoma (PC3; CRL-1435) and human healthy skin fibroblast (CCD-986Sk; CRL-1947) cell lines were examined. The cytotoxicity results showed that 2j, 3a, 3e, 3f are most active compounds in all cell lines (HT-29, MCF7, PC3, and CCD-986Sk).

Synthesis, computational studies and assessment of in vitro inhibitory activity of umbelliferon-based compounds against tumour-associated carbonic anhydrase isoforms IX and XII

Coumarins are widely diffused secondary metabolites possessing a plethora of biological activities. It has been established that coumarins represent a peculiar class of human carbonic anhydrase (hCA) inhibitors having a distinct mechanism of action involving a non-classical binding with amino acid residues paving the entrance of hCA catalytic site. Herein, we report the synthesis of a small series of new coumarin derivatives 7-11, 15, 17 prepared via classical Pechmann condensation starting from resorcinol derivatives and suitable β-ketoesters. The evaluation of inhibitory activity revealed that these compounds possessed nanomolar affinity and high selectivity towards tumour-associated hCA IX and XII over cytosolic hCA I and hCA II isoforms. To investigate the binding mode of these new coumarin-inspired inhibitors, the most active compounds 10 and 17 were docked within hCA XII catalytic cleft.

Evaluation of carbonic anhydrase and paraoxonase inhibition activities and molecular docking studies of highly water-soluble sulfonated phthalocyanines

The investigation of carbonic anhydrase and paraoxonase enzyme inhibition properties of water-soluble zinc and gallium phthalocyanine complexes ( 1 and 2 ) are reported for the first time. The binding of p-sulfonylphenoxy moieties to the phthalocyanine structure favors excellent solubilities in water, as well as providing an inhibition effect on carbonic anhydrase (CA) I and II isoenzymes and paraoxonase (PON1) enzyme. According to biological activity results, both complexes inhibited hCA I, hCA II, and PON1. Whereas 1 and 2 showed moderate hCA I and hCA II (off-target cytosolic isoforms) inhibitory activity (Ki values of 26.09 µM and 43.11 µM for hCA I and 30.95 µM and 33.19 µM for hCA II, respectively), they exhibited strong PON1 (associated with high-density lipoprotein [HDL]) inhibitory activity (Ki values of 0.37 µM and 0.27 µM, respectively). The inhibition kinetics were analyzed by Lineweaver-Burk double reciprocal plots. It revealed that 1 and 2 were noncompetitive inhibitors against PON1, hCA I, and hCA II. These complexes can be more advantageous than other synthetic CA and PON inhibitors due to their water solubility. Docking studies were carried out to examine the interactions between hCA I, hCA II, and PON1 inhibitors and metal complexes at a molecular level and to predict binding energies.

A Review on Anti-Tumor Mechanisms of Coumarins

Coumarins are a class of compound with benzopyrone as their basic structure. Due to abundant sources, easy synthesis, and various pharmacological activities, coumarins have attracted extensive attention from researchers. In particular, coumarins have very significant anti-tumor abilities and a variety of anti-tumor mechanisms, including inhibition of carbonic anhydrase, targeting PI3K/Akt/mTOR signaling pathways, inducing cell apoptosis protein activation, inhibition of tumor multidrug resistance, inhibition of microtubule polymerization, regulating the reactive oxygen species, and inhibition of tumor angiogenesis, etc. This review focuses on the mechanisms and the research progress of coumarins against cancers in recent years.

Inhibitory activity against carbonic anhydrase IX and XII as a candidate selection criterion in the development of new anticancer agents

Analysis of the literature data reveals that while inhibition of cancer-related carbonic anhydrase IX and XII isoforms continues to be an important enrichment factor for designing anticancer agent development libraries, exclusive reliance on the in vitro inhibition of these two recombinant isozymes in nominating candidate compounds for evaluation of their effects on cancer cells may lead not only to identifying numerous compounds devoid of the desired cellular efficacy but also to overlooking many promising candidates which may not display the best potency in biochemical inhibition assay. However, SLC-0111, now in phase Ib/II clinical trials, was developed based on the excellent agreement between the in vitro, in vivo and more recently, in-patient data.

An Overview of Coumarin as a Versatile and Readily Accessible Scaffold with Broad-Ranging Biological Activities

Privileged structures have been widely used as an effective template for the research and discovery of high value chemicals. Coumarin is a simple scaffold widespread in Nature and it can be found in a considerable number of plants as well as in some fungi and bacteria. In the last years, these natural compounds have been gaining an increasing attention from the scientific community for their wide range of biological activities, mainly due to their ability to interact with diverse enzymes and receptors in living organisms. In addition, coumarin nucleus has proved to be easily synthetized and decorated, giving the possibility of designing new coumarin-based compounds and investigating their potential in the treatment of various diseases. The versatility of coumarin scaffold finds applications not only in medicinal chemistry but also in the agrochemical field as well as in the cosmetic and fragrances industry. This review is intended to be a critical overview on coumarins, comprehensive of natural sources, metabolites, biological evaluations and synthetic approaches.

Overview on developed synthesis procedures of coumarin heterocycles

Considering highly valuable biological and pharmaceutical properties of coumarins, the synthesis of these heterocycles has been considered for many organic and pharmaceutical chemists. This review includes the recent research in synthesis methods of coumarin systems, investigating their biological properties and describing the literature reports for the period of 2016 to the middle of 2020. In this review, we have classified the contents based on co-groups of coumarin ring. These reported methods are carried out in the classical and non-classical conditions particularly under green condition such as using green solvent, catalyst and other procedures.

Tail approach synthesis of novel benzenesulfonamides incorporating 1,3,4-oxadiazole hybrids as potent inhibitor of carbonic anhydrase I, II, IX, and XII isoenzymes

Two new series of 1,3,4-oxadiazole benzenesulfonamide hybrids 3 and 4, having twenty novel compounds, have been designed and synthesized in order to assess their inhibition potential as CAIs against hCA I, II, IX, and XII. 'Tail approach' strategy has been used to design the aromatic sulfonamide scaffolds with carbonyl and amide linker. Excellent inhibitory activity against hCA I has been exhibited by compounds 3g and 4j, 3.5 magnitude of order better than reference drug AAZ (KI = 250 nM). Moreover, compound 4j (KI = 7.9 nM) effectively inhibited glaucoma-associated hCA II isoform as well as tumor-associated hCA IX isoform with KI = 16.3 nM. Further hCA XII was weakly inhibited by all the compounds with KI values ranging from 0.23 μM to 3.62 μM. Interestingly structure-activity relationship (SAR) study indicates that N-(3-nitrophenyl)-2-((5-(4-sulfamoylphenyl)-1,3,4-oxadiazol-2-yl)thio)acetamide (4j) is a potent compound to be investigated further for antiglaucoma and antitumor activity. The chemistry of the nature of different substitutions on the 1,3,4-oxadiazole bearing benzenesulfonamide substituted aromatic ring for potency and selectivity over one hCA isoform versus others is deliberated in the present study. In this context, the 1,3,4-oxadiazole motif can be a valuable tool worth developing for the procurement of novel and potent selective CAIs potentially useful for the management of a variety of diseases as chemotherapeutic agents.

Design, synthesis and biological evaluation of coumarin linked 1,2,4-oxadiazoles as selective carbonic anhydrase IX and XII inhibitors

A series of coumarin linked 1,2,4-oxadiazoles were synthesized and the synthesized compounds were subjected for evaluation against the four physiologically and pharmacologically relevant hCA isoforms, hCA I, II, IX and XII. Upon evaluation of the results, it was inferred that the coumarin linked 1,2,4-oxadiazoles showed selective hCA IX and XII inhibition (low to medium nanomolar range) over hCA I and II (>10000 nM). The inhibition constants ranged from low nanomolar to moderately nanomolar. Compounds 6o, 6a, 6q and 6c elicited hCA XII inhibition, with K_i values lower than that of the standard, Acetazolamide (AAZ) with compound 6o exhibiting a K_i value of 1 nM., against hCA IX, the compound 6c exhibited the most potent inhibition with a K_i value of 23.6 nM. Hence, compound 6o can be taken as an effective lead compound for the development of hCA XII inhibitors and compound 6c can be taken as a lead compound for the development of dual hCA IX and XII inhibitors. To understand the molecular interactions, the two most potent compounds 6a and 6o were docked within the hCA XII catalytic cleft in order to study their binding modes with that isoform.

Development of a cheminformatics platform for selectivity analyses of carbonic anhydrase inhibitors

The selectivity for a specific human Carbonic Anhydrase (hCA) isoform is an important property a hCA inhibitor (CAI) should be endowed with, in order to constitute a valuable therapeutic tool for the treatment of a desired pathology. In this context, we developed a chemoinformatic platform that allows the analysis of the structure and selectivity profile of known CAIs reported in literature, with the aim of identifying structural motifs connected to ligand selectivity, thus providing useful guidelines for the design of novel ligands selective for the desired hCA isoform. The platform is able to perform ultrafast structure and selectivity analyses through ligand fingerprint similarity, with no need of structural information about the target receptor and ligands' binding mode. It is easily accessible to the non-expert user through the implementation of a KNIME Analytic Platform workflow and could be extended to analyze the selectivity profile of known ligands of different target proteins.

Synthesis of coumarin-sulfonamide derivatives and determination of their cytotoxicity, carbonic anhydrase inhibitory and molecular docking studies

Carbonic anhydrases isoforms CA IX, and XII are known to be highly expressed in various human tissues and malignancies. CA IX is a prominent target for especially colorectal cancers, because it is overexpressed in colorectal cancer and this overexpression leads poor prognosis. Inhibition of CA IX activity by small molecule CA inhibitors like sulfonamides, sulfonamide derivative or coumarins leads to inhibition of tumorigenesis. Novel twenty-seven compounds in three series (sulfonamide-based imines (6a-6i), coumarin-based aldehydes (7a-7i), and coumarin-sulfonamide-based target molecules (8a-8i)) were synthesized and characterized by means of IR, NMR, and mass spectra. All compounds were tested for their ability to inhibit CA I, CA II, CA IX, and CA XII isoforms. 4-((((2-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-1,2,3-triazol-4-yl)methoxy)naphthalen-1-yl)-methylene)amino)methyl)benzenesulfonamide (8i) exhibited the highest hCA IX inhibition with the Ki of 45.5 nM. In addition, 8i was found to be potent in inhibiting cancer cell proliferation as selective (IC₅₀ = 17.01 ± 1.35 μM for HT-29, IC₅₀ = 118.73 ± 1.19 μM for HEK293T). This novel compound inhibited the CA IX and CA XII protein expression in HT-29 cells. These findings indicate that 8i can inhibit cellular proliferation in human colon cancer cells by specifically targeting the CA IX and CA XII expression.

Coumarin-containing hybrids and their anticancer activities

Cancer is the second leading cause of death worldwide, and it results in around 9 million deaths annually. The anticancer agents play an intriguing role in the treatment of cancers, while the severe anticancer scenario and the emergence of drug-resistant especially multidrug-resistant cancers create a huge demand for novel anticancer drugs with different mechanisms of action. The coumarin scaffold is ubiquitous in nature and is a highly privileged motif for the development of novel drugs due to its biodiversity and versatility. Coumarin derivatives can exert diverse antiproliferative mechanisms, and some of them such as Irosustat are under clinical trials for the treatment of various cancers, revealing their potential as putative anticancer drugs. Hybridization of coumarin moiety with other anticancer pharmacophores is a promising strategy to reduce side effects, overcome the drug resistance, and may provide valuable therapeutic intervention for the treatment of cancers. Thus, coumarin-containing hybrids occupy an important position in the development of novel anticancer agents. This review aims to summarize the recent advances made towards the development of coumarin-containing hybrids as potential anticancer agents, covering articles published between 2015 and 2019, and the structure-activity relationship together with mechanisms of action are also discussed.